1. Field of the Invention This invention relates to a two degree-of-freedom positioning and manipulating apparatus, and, more particularly, to a two degree-of-freedom manipulating apparatus constructed from two rotary drives.
2. Description of the Prior Art
First the term "degree of freedom" will be clarified with respect to a mechanical manipulating apparatus. Any object's attitude in three-dimensional space can be minimally described with 6 coordinate parameters: 3 of displacement and 3 of rotation. A manipulator with 2 degrees of freedom, then, can move an object in 2 of the 6 available coordinate space parameters.
In multiple degree-of-freedom manipulators and positioners, such as industrial robots, it is often desirous to locate the mechanical power sources, such as rotary electric or hydraulic motors, on a fixed frame coupled to, but not translated with, the manipulator. With the relatively heavy motors not translated with the manipulator, the manipulator apparatus can be made lighter and more agile than would otherwise be possible. Typically, with more than 1 degree of freedom, a transmission apparatus is required to deliver mechanical power from the fixed mounted source to the distally mounted manipulator members, such as the timing belt apparatus driving the second link on the SCARA (Selective Compliance Assembly Robot Arm) robot disclosed in U.S. Pat. No. 4,557,662.
It is also common in multiple degree-of-freedom manipulators to employ reduction drives to increase the usable level of motor power, to amplify the torque output of rotary motors, and to increase the manipulator's positioning precision.
U.S. Pat. No. 5,105,672 (Carson et. al.) discloses a precision rotary drive with particularly desirable performance characteristics consisting of a relatively large diameter cylindrical driven member coupled to a relatively small diameter cylindrical driver member through a cable system.